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The Power Grid

Ontarians use more than 152 terawatt hours of electricity a year. Ensuring that there is enough energy to meet that demand today and in the future is an ongoing and highly complex process. As the reliability coordinator for Ontario’s electricity system, the IESO is at the centre of it all.

Every five minutes, the IESO balances available supply with demand and directs the flow of electricity across the transmission system. At the same time, the IESO ensures that there is enough reserve energy available on short notice should there be a surge in demand or an unexpected equipment failure at one of the generators or on the transmission system.

The IESO also monitors the system and identifies what is required to maintain reliability in the future, reporting on these recommendations through regular publications. In its quarterly 18-month forecasts of the growth in demand for electricity, the IESO assesses whether there will be adequate generation and transmission facilities. In addition, the IESO prepares the semi-annual Ontario Reliability Outlook, which reports on the progress of interrelated generation, transmission and demand-side projects underway to meet Ontario's reliability requirements.

The IESO coordinates emergency preparedness for the province's electricity system and played a key role in managing the restoration of power following the August 2003 blackout.

Finally, the IESO has full statute-based authority for establishing, monitoring and enforcing reliability standards in the province. All the companies that make up the power system in Ontario must meet the IESO's standards. An audit by the North American Electricity Reliability Council cited the IESO as a model for system operators, while a peer review showed that its practices in enforcing reliability are exemplary.
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